As used herein, the term “magnetic field sensing element” is used to describe a variety of electronic elements that can sense a magnetic field. One such magnetic field sensing element is a magnetoresistance (MR) element. The magnetoresistance element has a resistance that changes in relation to a magnetic field experienced by the magnetoresistance element.
As is known, there are different types of magnetoresistance elements, for example, a semiconductor magnetoresistance element such as Indium Antimonide (InSb), a giant magnetoresistance (GMR) element, an anisotropic magnetoresistance element (AMR), and a tunneling magnetoresistance (TMR) element, also called a magnetic tunnel junction (MTJ) element.
As is known, metal based or metallic magnetoresistance elements (e.g., GMR, TMR, AMR) tend to have axes of sensitivity parallel to a substrate on which they are formed.
As used herein, the term “magnetic field sensor” is used to describe a circuit that uses a magnetic field sensing element, generally in combination with other circuits. In a typical magnetic field sensor, the magnetic field sensing element and the other circuits can be integrated upon a common substrate.
Magnetic field sensors are used in a variety of applications, including, but not limited to, an angle sensor that senses an angle of a direction of a magnetic field, a current sensor that senses a magnetic field generated by a current carried by a current-carrying conductor, a magnetic switch that senses the proximity of a ferromagnetic object, a rotation detector that senses passing ferromagnetic articles, for example, magnetic domains of a ring magnet or a ferromagnetic target (e.g., gear teeth) where the magnetic field sensor is used in combination with a back-biased or other magnet, and a magnetic field sensor that senses a magnetic field density of a magnetic field.
GMR and TMR elements are known to have a relatively high sensitivity, compared, for example, to Hall elements. GMR and TMR elements are also known to have moderately good linearity, but over a restricted range of magnetic fields, more restricted in range than a range over which a Hall element can operate.
The magnetoresistance element may be a single element or, alternatively, two or more magnetoresistance elements may be arranged in various configurations, e.g., a half bridge or full (Wheatstone) bridge.
When arranged in a half bridge, usually one magnetoresistance element is used in series combination with one fixed resistor. If instead, two identical magnetoresistance elements were used, the half bridge would tend to have no output signal, since both magnetoresistance elements would tend to change resistance in the same direction in response to a magnetic field.
When arranged in a full bridge, usually two magnetoresistance elements are used in two series combinations with two fixed resistors. If instead, four identical magnetoresistance elements were used, the full bridge would tend to have no output signal, since the four magnetoresistance elements would tend to change resistance in the same direction in response to a magnetic field.
The above-described bridges that use fixed resistors in various arrangements have disadvantages. For example, the fixed resistors can have temperature coefficients that do not match the temperature coefficients of the magnetoresistance elements, and therefore, an output signal generated by the bridges may vary with respect to temperature.
Even a single magnetoresistance element driven from a current source (high output impedance) has a temperature coefficient that results in an output signal generated by the single magnetoresistance element that may vary with respect to temperature.
It would be desirable to provide a magnetoresistance element, half bridge, or full bridge, an output signal from which varies less with temperature. It would be desirable to provide a magnetic field sensor that uses the above described magnetoresistance element, half bridge, or full bridge.